Absorbent Article Comprising A Fibrous Structure Comprising Synthetic Fibers And A Hydrophilizing Agent

ABSTRACT

An absorbent article comprising a nonwoven fibrous structure comprising a plurality of synthetic fibers. The synthetic fibers may be associated with one or more hydrophilizing agents. A process for making the nonwoven fibrous structure involves association of the synthetic fibers with one or more hydrophilizing agents.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. application Ser. No.11/731,596 filed on Mar. 30, 2007; which claimed the benefit of U.S.Provisional Application No. 60/788,620 filed on Apr. 3, 2006 and U.S.Provisional Application No. 60/788,417, filed on Mar. 31, 2006, thesubstance of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to absorbent articles comprising fibrousstructures comprising synthetic fibers. The synthetic fibers may furtherbe associated with a hydrophilizing agent.

BACKGROUND OF THE INVENTION

Disposable absorbent articles, such as diapers, adult incontinenceproducts, and feminine hygiene products, are well known in the art. Suchdisposable articles collect and retain urine, menses and fecal materialdeposited thereon by the wearer.

Fibrous structures, such as paper webs, are well known in the art andare in common use today for absorbent articles, for example, as topsheetmaterial or as a core cover to enclose the absorbent core. Variousnatural fibers, including cellulose fibers, as well as a variety ofsynthetic fibers, have been employed in papermaking. Typical tissuepaper may be comprised primarily of natural fibers. The overwhelmingmajority of the natural fibers used in tissue may be derived from trees.Many species may be used, including long fiber containing softwoods(conifer or gymnosperms) and short fiber containing hardwoods (deciduousor angiosperms).

Despite a broad range of natural fiber types, natural fibers derivedfrom trees may be limiting when used exclusively in disposable tissueand towel products. Wood fibers may be high in dry modulus andrelatively large in diameter, which may cause their flexural rigidity tobe higher than desired for some uses. Such high-rigidity fibers mayproduce stiff non-soft tissue. Further, wood fibers can have theundesirable characteristic of having a relatively high stiffness whendry, which may negatively affect the softness of the product and mayhave low stiffness when wet due to hydration, which may cause poorabsorbency of the resulting product. Wood-based fibers may also belimiting because the geometry or morphology of the fibers cannot be“engineered” to any great extent.

The use of synthetic fibers that have the ability to thermally fuse toone another and/or to natural fibers is an excellent way to overcome thepreviously mentioned limitations of natural fibers. Wood-based naturalfibers are not thermoplastic and hence cannot thermally bond to otherfibers. Synthetic thermoplastic polymers can be formed into fibers witha range of diameters, including very small fibers. Further, syntheticfibers can be formed to be lower modulus than natural fibers. Thus, asynthetic fiber can be made with very low flexural rigidity, which mayincrease product softness. In addition, functional cross-sections of thesynthetic fibers can be micro-engineered during the spinning process.Synthetic fibers can also be designed to maintain modulus when wetted,and hence webs made with such fibers may resist collapse duringabsorbency tasks. Further, the use of synthetic fibers can aid in theformation of a web and/or its uniformity. Accordingly, the use ofthermally bonded synthetic fibers in tissue and towel products canresult in a strong network of highly flexible fibers (good for softness)joined with water-resistant high-stretch bonds (good for softness andwet strength).

The use of synthetic fibers, however, may have some limitations. Thesynthetic fibers may have a general characteristic of being hydrophobic.As such, the suspension of the hydrophobic synthetic fibers in a fluidcarrier during the papermaking process may result in a slurry in whichthe hydrophobic synthetic fibers have clumped together. A fibrousstructure created from such a slurry may demonstrate areas of highstiffness when dry and low stiffness when wet. Thus, the benefits ofutilizing synthetic fibers to maintain the modulus of the fibrousstructure when wet may not be realized. Additionally, the hydrophobiccharacter of the synthetic fibers may overcome the generally hydrophiliccharacter of the natural fibers. This, in turn, may have a negativeimpact on the fibrous structure and may result in a decrease inabsorbency and/or rate of absorption of the overall structure.

Fibrous structures are usually hydrophobic, as noted above. However, formany applications in hygiene products, such as absorbent articles, it isnecessary to have hydrophilic fibrous structures. Therefore, the fibrousstructure has to be treated accordingly.

One typical component of disposable absorbent articles is a core cover.A core cover may typically be a nonwoven material designed to containthe absorbent core and provide structural integrity when the absorbentcore is wet or dry. The core cover may be a tissue wrap, or a nonwovenmaterial which has been rendered hydrophilic.

A common method for rendering nonwoven fibrous structures hydrophilic iscoating the surface of the nonwoven fibrous structure with hydrophilicsurfactants. As this coating does not lead to a tight chemical bondbetween the nonwoven fibrous structure and the surfactant, thesurfactant can be washed off during use when the absorbent article iswetted. The decrease in liquid strike-through time is a desirable effectwhen the fibrous structure is coated with surfactant. Liquidstrike-through refers to liquid passing through the fibrous structurewith liquid strike-through time referring to the time it takes for acertain amount of liquid to pass through the fibrous structure. However,as the surfactant is washed off when the coated fibrous structures areexposed to the liquid, the strike-through time in the next gush isincreased. This results in performance reduction during use on diapersor other articles comprising such fibrous structures. Furthermore, atthe same time as liquid strike-through time decreases due to use ofsurfactants, surface tension of the liquid, which was in contact withthe fibrous structure, is reduced. This reduction is undesirable,because it can cause increased urine leakage in a diaper.

Another common method to render a fibrous structure hydrophilic is byapplying corona and/or plasma treatment. Plasma is an ionized form ofgas that can be obtained by ionizing a gas or liquid medium. Plasmas arewidely used for the treatment of organic and inorganic materials topromote adhesion between various materials. Polymers that havechemically inert surfaces with low surface energies do not allow goodcoatings with bondings and adhesives. Thus, these surfaces are treatedto make them receptive to bonding with other substrates, coatings,adhesives and printing inks. However, corona and plasma treatments leadto low coating durability upon storage of the treated material, i.e.,hydrophilicity decreases over time.

A wide variety of hydrophilizing agents for use in domestic andindustrial fabric treatment processes such as laundering, fabric dryingin hot air clothes dryers, and the like, are known in the art and areconventionally referred to in those fields as “Soil Release Polymers”(SRP's) or “Soil Release Agents” (SRA's). Various oligomeric orpolymeric hydrophilizing agents have been commercialized and are knownfor their use as soil release compounds in detergent compositions andfabric softener/antistatic articles and compositions. Hydrophilizingagents utilized in laundry applications generally are employed to pre-or post-treat woven fabrics. Woven fabrics pre-treated withhydrophilizing agents may exhibit stain guard characteristics whilewoven fabrics post-treated with hydrophilizing agents may exhibit stainrelease characteristics. The woven fabrics may be washed and re-washedand may retain their stain guard and stain release characteristics. Suchhydrophilizing agents which comprise an oligomeric or polymeric ester“backbone” are sometimes referred to as “Soil Release Esters” (SRE's).

Hydrophilizing agents may also associate with synthetic fibers in anonwoven fibrous structure. It has now been found that the use of ahydrophilizing agent to associate with the synthetic fibers of anonwoven fibrous structure may have the ability to overcome one or moreof the above mentioned disadvantages associated with the use ofsynthetic fibers. It has now been found that the association of thehydrophilizing agents with synthetic fibers may enable the syntheticfibers to display hydrophilic characteristics thus overcoming thegeneral hydrophobic nature of the synthetic fibers. This may allow forthe dispersion of the synthetic fibers throughout the nonwoven fibrousstructure instead of clumping together and may help provide a morehomogeneous distribution of the fibers in webs which also comprisenatural fibers. A uniform distribution of synthetic fibers which haveassociated with hydrophilizing agents in combination with natural fibersmay also result in a fibrous structure that is hydrophilic in nature. Afibrous structure that is hydrophilic in nature may exhibit an increasein the absorbency and/or rate of absorption of fluids. Therefore, theutilization of hydrophilizing agents may result in a positive impact onthe absorbency and/or rate of absorption of the nonwoven fibrousstructure.

Absorbent articles, such as diapers, adult incontinence products, andfeminine hygiene products, are well known articles of staplemanufacturing. Multiple attempts have been made to provide them with anoverall good fit and with a high absorbent capacity. Modern absorbentarticles may make use of absorbent polymer materials or so-calledsuperabsorbent materials. The absorbent polymer materials are generallysurrounded by nonwoven materials. Many nonwoven materials thatincorporate synthetic fibers are hydrophobic. The performance ofabsorbent polymer materials surrounded by a hydrophobic fibrousstructure may be negatively affected as fluid may not be absorbed asreadily by the polymer material if repulsed by the surroundinghydrophobic fibrous structure.

It would be desirable to provide improved fibrous structures comprisingsynthetic fibers in association with hydrophilizing agents. It would bedesirable to provide a fibrous structure in which the synthetic fibersexhibit hydrophilic characteristics. It would be desirable to provide afibrous structure in which the synthetic fibers are dispersed throughoutthe fibrous structure. It would be desirable to provide a fibrousstructure in which absorbency is not negatively impacted. It would bedesirable to utilize such a fibrous structure in an absorbent article toenhance performance of the absorbent article. It would be desirable toprovide an absorbent article in which the rate of absorption isacceptable to consumers of the absorbent article.

SUMMARY OF THE INVENTION

The present invention relates to an absorbent article comprising anonwoven fibrous structure comprising plurality of synthetic fibers anda hydrophilizing agent. The synthetic fibers and the hydrophilizingagent may comprise a durable association.

In one example of the present invention, an absorbent article comprisinga nonwoven fibrous structure comprising 1) a plurality of syntheticfibers, wherein one or more (or each) of said synthetic fibers comprisesa polymer, and 2) a hydrophilizing agent, wherein said polymer and saidhydrophilizing agent comprise complementary segments that are associatedwith one another, is provided.

The synthetic fibers of the fibrous structure may comprise a polymer.The polymer and the hydrophilizing agent may comprise complementarysegments that may associated with one another. At least one of thecomplementary segments may comprise a polyester segment. The polymer ofthe synthetic fiber may comprise material selected from the groupconsisting of polyesters, polyamides, polyhydroxyalkanoates,polysaccharides, and combinations thereof. The fibrous structure mayfurther comprise a plurality of natural fibers.

The hydrophilizing agent may be a copolymer. The hydrophilizing agentmay be selected from the group consisting of polyester,poly(ethoxylate), polyethylene oxide, polyoxyethylene, polyethyleneglycol, polypropylene glycol, terephthalate, polypropylene oxide,polyethylene terephthalate, polyoxyethylene terephthalate, ethoxylatesiloxane and combinations thereof. The hydrophilizing agent may havefrom about 1 to about 15 ethoxylated groups.

The nonwoven fibrous structure may further comprise binder material. Thebinder material may be selected from the group consisting of permanentwet strength resins, temporary wet strength resins, dry strength resins,latex binders and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cut-away top plan view of a disposable absorbentarticle including an absorbent core and a core cover.

FIG. 2 is a partial sectional view along 2-2 of one alternativeembodiment of the absorbent core of the disposable absorbent article ofFIG. 2.

FIG. 3 depicts an artist's conception of the association of a dimerichydrophilizing agent and a synthetic fiber.

FIG. 4 depicts a schematic plan view of an embodiment of a fibrousstructure of the present invention in which the synthetic fibers aredistributed in a non-random pattern.

FIG. 5 depicts a schematic plan view of an embodiment of a fibrousstructure of the present invention in which the synthetic fibers andnatural fibers are distributed randomly throughout the fibrousstructure.

FIG. 6 is a schematic top view of a strike through plate which may beused to measure Liquid Strike Through of a substrate.

FIG. 7 is a section view along 9-9 of the strike through place of FIG.6.

FIG. 8 is a sectional perspective view along 10-10 of the strike throughplate of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the following terms have the following meanings.

“Basis weight” refers to the weight (measured in grams) of a unit area(typically measured in square meters) of the fibrous structure, whichunit area is taken in the plane of the fibrous structure. The size andshape of the unit area from which the basis weight is measured isdependent upon the relative and absolute sizes and shapes of the regionshaving different basis weights.

“Binder” and/or “Binder material” refers to the various wet and drystrength resins and retention aid resins known in the paper making art.

“Coarseness” refers to the weight per unit length of fiber expressed asmilligrams per 100 m, as set forth in TAPPI Method T 234 cm-02.

“Hydrophilizing agent” may be broadly disclosed as comprising oligomericor polymeric “Backbones” to which are appended hydrophilic substituents.“Oligomeric” herein refers to a polymer molecule with fewer than 10repeating units such as dimers, trimers, tetramers, etc. “Polymeric”herein refers to a molecule with greater than 10 repeating units. A widevariety of such agents are, as noted above, very well known for use assoil release compounds in the detergency arts. The manufacture of suchagents forms no part of this invention. Reference can be made to aseries of patents more fully disclosing such compounds, as well as theirmethod of synthesis, as disclosed hereinafter. The present inventionemploys such compounds, and their equivalents, in the improved nonwovenfibrous structure described herein. Such compounds are usuallywater-soluble or water-dispersible under the preferred usage conditionsherein, e.g., in a fiber slurry comprising an aqueous carrier medium;20° C.-90° C. operating conditions; usage levels of about 0.001% toabout 20%, by weight of the fiber weight; weight ratio of hydrophilizingagent: hydrophobic fiber in slurry in the range of from about 0.0001:1to about 1:1.

“Nonwoven” refers to a fibrous structure made from an assembly ofcontinuous fibers, co-extruded fibers, non-continuous fibers, andcombinations thereof, without weaving or knitting, by processes such asspun-bonding, carding, melt-blowing, air-laying, wet-laying, co-form, orother processes known in the art for such purposes. The non-wovenstructure may comprise one or more layers of such fibrous assemblies,wherein each layer may include continuous fibers, co-extruded fibers,non-continuous fibers, and combinations thereof.

“Unitary fibrous structure” or “fibrous structure” refers to anarrangement comprising a plurality of synthetic fibers that areinter-entangled to form a single-ply sheet product having certainpre-determined microscopic geometric, physical, and aestheticproperties. The fibrous structure may further comprise natural fibers.The synthetic and/or natural fibers may be layered, as known in the art,in the unitary fibrous structure. The fibrous structure may benon-woven. The fibrous structure may be useful as a web for tissuegrades of paper (i.e., sanitary tissue products) such as toilet paper,paper towels, napkins, facial tissue, sanitary products such as wipes,and absorbent articles such as diapers, feminine pads and incontinencearticles. The fibrous structure of the present invention may beincorporated into an article, such as a single or multi-ply sanitarytissue product. The fibrous structure of the present invention may belayered or may be homogeneous.

Fibrous Structure

The fibrous structure of the present invention may take a number ofdifferent forms. The fibrous structure may comprise 100% syntheticfibers or may be a combination of synthetic fibers and natural fibers.In one embodiment of the present invention, the fibrous structure mayinclude one or more layers of a plurality of synthetic fibers mixed witha plurality of natural fibers. The synthetic fiber/natural fiber mix maybe relatively homogeneous in that the different fibers may be dispersedgenerally randomly throughout the layer. The fiber mix may be structuredsuch that the synthetic fibers and natural fibers may be disposedgenerally non-randomly. In one embodiment, the fibrous structure mayinclude at least one layer comprising a plurality of natural fibers andat least one adjacent layer comprising a plurality of synthetic fibers.In another embodiment, the fibrous structure may include at least onelayer that comprises a plurality of synthetic fibers homogeneously mixedwith a plurality of natural fibers and at least one adjacent layer thatcomprises a plurality of natural fibers. In an alternate embodiment, thefibrous structure may include at least one layer that comprises aplurality of natural fibers and at least one adjacent layer that maycomprise a mixture of a plurality of synthetic fibers and a plurality ofnatural fibers in which the synthetic fibers and/or natural fibers maybe disposed generally non-randomly. Further, one or more of the layersof mixed natural fibers and synthetic fibers may be subjected tomanipulation during or after the formation of the fibrous structure todisperse the layer or layers of mixed synthetic and natural fibers in apredetermined pattern or other non-random pattern. Such a pattern may bea repeating pattern.

Examples of natural fibers may include cellulosic natural fibers, suchas fibers from hardwood sources, softwood sources, or other non-woodplants. The natural fibers may comprise cellulose, starch andcombinations thereof. Non-limiting examples of suitable cellulosicnatural fibers include wood pulp, typical northern softwood Kraft,typical southern softwood Kraft, typical CTMP, typical deinked, cornpulp, acacia, eucalyptus, aspen, reed pulp, birch, maple, radiata pineand combinations thereof. Other sources of natural fibers from plantsinclude, but are not limited to, albardine, esparto, wheat, rice, corn,sugar cane, papyrus, jute, reed, sabia, raphia, bamboo, sidal, kenaf,abaca, sunn, rayon, lyocell, cotton, hemp, flax, ramie and combinationsthereof. Yet other natural fibers may include fibers from other naturalnon-plant sources, such as, down, feathers, silk, and combinationsthereof. The natural fibers may be treated or otherwise modifiedmechanically or chemically to provide desired characteristics or may bein a form that is generally similar to the form in which they can befound in nature. Mechanical and/or chemical manipulation of naturalfibers does not exclude them from what are considered natural fiberswith respect to the development described herein.

The synthetic fibers can be any material, such as, but not limited to,those selected from the group consisting of polyesters, polypropylenes,polyethylenes, polyethers, polyamides, polyhydroxyalkanoates,polysaccharides, and combinations thereof. The synthetic fibers maycomprise a polymer. The polymer may be any material such as, but notlimited to, those materials selected from the group consisting ofpolyesters, polyamides, polyhydroxyalkanoates, polysaccharides, andcombinations thereof. More specifically, the material of the polymersegment may be selected from the group consisting of poly(ethyleneterephthalate), poly(butylene terephthalate),poly(1,4-cyclohexylenedimethylene terephthalate), isophthalic acidcopolymers (e.g., terephthalate cyclohexylene-dimethylene isophthalatecopolymer), ethylene glycol copolymers (e.g., ethylene terephthalatecyclohexylene-dimethylene copolymer), polycaprolactone, poly(hydroxylether ester), poly(hydroxyl ether amide), polyesteramide, poly(lacticacid), polyhydroxybutyrate, and combinations thereof. The polymer maycomprise a segment, such as a polymer segment that may be complementaryto a hydrophilizing agent and/or a segment thereof. The portion of thepolymer segment that may be complementary to a hydrophilizing agent mayfacilitate association between the synthetic fiber and thehydrophilizing agent. The complementary segment may comprise a polyestersegment. The polyester segment may further comprise a polyethyleneterephthalate segment. The complementary segment of the polymer may belocated on the surface of the synthetic fiber. Such may be the situationwherein the synthetic fiber may be a bicomponent fiber comprising a coreand an outer surface.

Further, the synthetic fibers can be a single component (i.e., singlesynthetic material or mixture makes up entire fiber), bi-component(i.e., the fiber is divided into regions, the regions including two ormore different synthetic materials or mixtures thereof and may includeco-extruded fibers) and combinations thereof. It is also possible to usebicomponent fibers, or simply bicomponent or sheath polymers. Thesebicomponent fibers can be used as a component fiber of the structure,and/or they may be present to act as a binder for the other fiberspresent in the nonwoven material. Any or all of the synthetic fibers maybe treated before, during, or after the process of the present inventionto change any desired properties of the fibers. For example, in certainembodiments, it may be desirable to treat the synthetic fibers before orduring the papermaking process to make them more hydrophilic, morewettable, etc.

In certain embodiments of the present invention, it may be desirable tohave particular combinations of fibers to provide desiredcharacteristics. For example, it may be desirable to have fibers ofcertain lengths, widths, coarseness or other characteristics combined incertain layers or separate from each other. The fibers may have anaverage fiber length of greater than about 0.20 mm. The fibers may havean average fiber length of from about 0.20 mm to about 10.0 mm. Thefibers may have an average fiber width of greater than about 5micrometers. The fibers may have an average fiber width of from about 5micrometers to about 50 micrometers. The fibers may have a coarseness ofgreater than about 5 mg/100 m. The fibers may have a coarseness of fromabout 5 mg/100 m to about 75 mg/100 m. Individually, the fibers may havecertain desired characteristics.

The fibrous structure may further comprise a binder material. Thefibrous structure may comprise from about 0.01% to about 1%, 3%, or 5%by weight of a binder material selected from the group consisting ofpermanent wet strength resins, temporary wet strength resins, drystrength resins, retention aid resins and combinations thereof.

If permanent wet strength is desired, the binder material may beselected from the group consisting of polyamide-epichlorohydrin,polyacrylamides, styrene-butadiene latexes, insolubilized polyvinylalcohol, ureaformaldehyde, polyethyleneimine, chitosan polymers andcombinations thereof.

If temporary wet strength is desired, the binder material may beselected from the groups of starch-based temporary wet strength resinsconsisting of cationic dialdehyde starch-based resin, dialdehyde starchand combinations thereof. The resin described in U.S. Pat. No. 4,981,557may also be used.

If dry strength is desired, the binder material may be selected from thegroup consisting of polyacrylamide, starch, polyvinyl alcohol, guar orlocust bean gums, polyacrylate latexes, carboxymethyl cellulose andcombinations thereof.

A latex binder material may also be utilized. Such a latex binder mayhave a glass transition temperature from about 0° C., −10° C., or −20°C. to about −40° C., −60° C., or −80° C. Examples of latex binders thatmay be used include, but are not limited to, polymers and copolymers ofacrylate esters, referred to generally as acrylic polymers, vinylacetate-ethylene copolymers, styrene-butadiene copolymers, vinylchloride polymers, vinylidene chloride polymers, vinylchloride-vinylidene chloride copolymers, acrylo-nitrile copolymers,acrylic-ethylene copolymers and combinations thereof. The wateremulsions of these latex binders usually contain surfactants. Thesesurfactants may be modified during drying and curing so that they becomeincapable of rewetting.

Methods of application of the binder material may include aqueousemulsion, wet end addition, spraying and printing. At least an effectiveamount of binder material may be applied to the fibrous structure.Between about 0.01% and about 1.0%, 3.0% or 5.0% may be retained on thefibrous structure, calculated on a dry fiber weight basis. The bindermaterial may be applied to the fibrous structure in an intermittentpattern generally covering less than about 50% of the surface area ofthe structure. The binder material may also be applied to the fibrousstructure in a pattern to generally cover greater than about 50% of thefibrous structure. The binder material may be disposed on the fibrousstructure in a random distribution. Alternatively, the binder materialmay be disposed on the fibrous structure in a non-random repeatingpattern.

Additional information relating to the fibrous structure may be found inU.S. Patent Publication Nos. 2004/0154768 and 2004/0157524, U.S. Pat.Nos. 4,588,457; 5,397,435; and 5,405,501.

A variety of products can be made using the fibrous structure of thepresent invention. The resultant products may be disposable. Theresultant products may find use in filters for air, oil and water;vacuum cleaner filters; furnace filters; face masks; coffee filters, teaor coffee bags; thermal insulation materials and sound insulationmaterials; nonwovens for absorbent articles such as diapers, femininepads, and incontinence articles; biodegradable textile fabrics forimproved moisture absorption and softness of wear such as microfiber orbreathable fabrics; an electrostatically charged, structured web forcollecting and removing dust; reinforcements and webs for hard grades ofpaper, such as wrapping paper, writing paper, newsprint, corrugatedpaper board, and webs for tissue grades of paper such as toilet paper,paper towel, napkins, and facial tissue; medical uses such as surgicaldrapes, wound dressing, bandages, and dermal patches. The fibrousstructure may also include odor absorbents, termite repellents,insecticides, rodenticides, and the like, for specific uses. Theresultant product may absorb water and oil and may find use in oil orwater spill clean-up, or controlled water retention and release foragricultural or horticultural applications.

Absorbent Article

The fibrous structure, as described above, may be utilized to form acomponent of an absorbent article. “Absorbent article” refers to deviceswhich may absorb and may contain bodily exudates, and, morespecifically, refers to devices which may be placed against or inproximity to the body of the wearer to absorb and contain the variousexudates discharged from the body. This may include, but is not limitedto, urine, menses and vaginal discharges, sweat and feces. Examples ofillustrative disposable absorbent articles include but are not limitedto, diapers, adult incontinence products, training pants, femininehygiene pads, panty liners and the like.

FIG. 1 is a plan view of a disposable absorbent article, specifically adiaper 20. The diaper 20 is shown in its flat out, uncontracted state(i.e., without elastic induced contraction). Portions of the structureare cut away to show the underlying structure of the diaper 20,including the absorbent core 10. The portion of the diaper 20 thatcontacts a wearer is facing the viewer. The chassis 22 of the diaper 20in FIG. 1 may comprise the main body of the diaper 20. The chassis 22may comprise an outer covering including a liquid pervious topsheet 24and/or a liquid impervious backsheet 26. The chassis 22 may also includemost or all of the absorbent core 10 encased between the topsheet 24 andthe backsheet 26.

The chassis 22 may comprise the main structure of the diaper 20 withother features added to form the composite diaper structure. Thetopsheet 24, backsheet 26, and absorbent core 10 may include manydifferent materials and may be assembled in a variety of well knownconfigurations, exemplary diaper materials and configurations aredescribed generally in U.S. Pat. Nos. 3,860,003; 5,151,092; 5,221,274;5,569,234 and 6,004,306.

Any topsheet compatible with the present invention which is known in theart can be used in the present invention. A suitable material for atopsheet may be manufactured from a wide range of materials, such asporous foams, reticulated foams, apertured plastic films, or woven ornonwoven materials of natural fibers (e.g., wood or cotton fibers),synthetic fibers (e.g., polyester or polypropylene fibers), or acombination of natural and synthetic fibers. As an example, a materialsuitable for use in a topsheet comprises a web of staple-lengthpolypropylene fibers is manufactured by Veratec, Inc., a Division ofInternational Paper Company, of Walpole, Mass. under the designationP-8.

Some examples of suitable topsheets are described further in U.S. Pat.Nos. 3,929,135; 4,324,246; 4,342,314; 4,463,045; 5,006,394; 4,609,518;and 4,629,643. Any portion of the topsheet may be coated with a lotionas is known in the art. Examples of suitable lotions include thosedescribed in U.S. Pat. Nos. 5,607,760; 5,609,587; 5,635,191; 5,643,588;5,968,025; 6,716,441; and PCT Publication No. WO 95/24173.

The topsheet 24 in FIG. 1 may be fully or partially elasticized or maybe foreshortened to provide a void space between the topsheet 24 and theabsorbent core 10. Exemplary structures including elasticized orforeshortened topsheets are described in more detail in U.S. Pat. Nos.4,892,536; 4,990,147; 5,037,416 and 5,269,775.

The backsheet 26 in FIG. 1 may generally be the portion of the diaper 20positioned with the absorbent core 10 between the backsheet 26 and thetopsheet 24. The backsheet 26 may be joined with the topsheet 24. Thebacksheet 26 may prevent the exudates absorbed by the absorbent core 10and contained within the diaper 20 from soiling other external articlesthat may contact the diaper 20, such as bed sheets and undergarments.The backsheet 26 may be substantially impervious to liquids (e.g.,urine) and may comprise a laminate of a nonwoven and a thin plastic filmsuch as a thermoplastic film having a thickness of between about 0.012mm (0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheet films mayinclude those manufactured by Tredegar Industries Inc. of Terre Haute,Ind. and sold under the trade names X15306, X10962, and X10964. Othersuitable backsheet materials may include breathable materials thatpermit vapors to escape from the diaper 20 while still preventingexudates from passing through the backsheet 26. Exemplary breathablematerials may include materials such as woven webs, nonwoven webs,composite materials such as film-coated nonwoven webs, and microporousfilms such as manufactured by Mitsui Toatsu Co., of Japan under thedesignation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex.,under the designation EXXAIRE. Suitable breathable composite materialscomprising polymer blends are available from Clopay Corporation,Cincinnati, Ohio under the name HYTREL blend P18-3097.

Diapers according to the present invention may be provided with are-closable fastening system which may include at least one fasteningmember and at least one stored landing zone. In order to keep the diaperin place about the wearer, a portion of the first waist region may beattached by a fastening member to a portion of the second waist region,thereby forming leg opening(s) and a waist. Alternatively, the diapermay be provided in the form of pant-type diapers. The diaper may alsoinclude such other features as are known in the art including waist capfeatures, elastics and the like to provide better fit, containment andaesthetic characteristics. The chassis may further include side panels,elasticized leg cuffs, and an elastic waist feature, wherein the legcuffs and the elastic waist feature each typically comprise elasticmembers. One end portion of the diaper may be configured as a firstwaist region of the diaper. The opposite end portion may be configuredas a second waist region of the diaper. An intermediate portion of thediaper may be configured as a crotch region, which may extendlongitudinally between the first and second waist regions. The waistregions may include elastic elements such that they gather about thewaist of the wearer to provide improved fit and containment. The crotchregion may be that portion of the diaper which, when the diaper is worn,is generally positioned between the wearer's legs. Additional detailsregarding the waist features and cuffs may be found in U.S. Pat. Nos.3,860,003; 4,515,595; 4,695,278; 4,909,803; 5,151,092; and 5,221,274.

The diaper 20 may include front ears and back ears. The front and/orback ears may be unitary elements of the diaper 20 (i.e., they are notseparately manipulative elements secured to the diaper 20, but ratherare formed from and are extensions of one or more of the various layersof the diaper). In certain embodiments, the front and/or back ears maybe discrete elements that are joined to the chassis 22, as shown inFIG. 1. In other embodiments, the front and/or back ears may comprise adiscrete element joined to the chassis 22 with the chassis 22 having alayer, element, or substrate that extends over the front and/or backear. The front ears and back ears may be extensible, inextensible,elastic, or inelastic. The front and/or back ears may also be subjectedto activation, mechanical activation, ring rolling, etc. as described inU.S. Pat. Nos. 5,167,897; 5,143,679; 5,156,793; 5,705,013; 5,683,533;and 5,580,411. The term “activation” or “activating” refers herein tothe process of making a nonwoven, or an elastic and nonwoven laminatemore extensible.

The absorbent article may comprise an absorbent core that may beprimarily responsible for fluid handling properties of the article,including acquiring, transporting, distributing and storing body fluids.As such, the absorbent core typically does not include the topsheet orbacksheet of the absorbent article. The absorbent core 10 in FIG. 1generally is disposed between the topsheet 24 and the backsheet 26. Theabsorbent core 10 may comprise a core cover 42 and a storage layer 60 asshown in FIG. 2. The storage layer 60 may comprise any absorbentmaterial that is generally compressible, conformable, non-irritating tothe wearer's skin, and capable of absorbing and retaining liquids suchas urine and other certain body exudates. The storage layer 60 maycomprise a wide variety of liquid-absorbent materials commonly used indisposable diapers and other absorbent articles such as comminuted woodpulp, which is generally referred to as air felt or fluff. Examples ofother suitable absorbent materials include creped cellulose wadding;melt blown polymers, including co-form; chemically stiffened, modifiedor cross-linked cellulosic fibers as described in U.S. Pat. No.5,137,537; tissue, including tissue wraps and tissue laminates,absorbent foams, absorbent sponges, superabsorbent polymers (such assuperabsorbent fibers) such as those described in U.S. Pat. No.5,599,335; absorbent gelling materials, or any other known absorbentmaterial or combinations of materials. Examples of some combinations ofsuitable absorbent materials are fluff with absorbent gelling materialsand/or superabsorbent polymers, and absorbent gelling materials andsuperabsorbent fibers etc. In one optional embodiment the storage layeris air felt free, that is, it contains no air felt. The storage layermay further comprise minor amounts (typically less than 10%) ofnon-liquid absorbent materials, such as adhesives, waxes, oils and thelike.

The storage layer of the absorbent core may comprise absorbent polymermaterial. The absorbent polymer material may also be mixed withabsorbent fibrous material, such as airfelt material, which can providea matrix for immobilization of the super-absorbent polymer material.However, a relatively low amount of fibrous cellulose material may beused, such as less than about 40%, 20% or 10% weight of cellulosefibrous material as compared to the weight of absorbent polymermaterial. Substantially airfelt free cores may be useful as well.

Optionally, the storage layer of the absorbent core can also comprise anabsorbent fibrous material, for example cellulose fibers. This fibrousmaterial can be pre-mixed with the absorbent polymeric material and belaid down in one process step or it can alternatively be laid-down inseparate process steps.

Additionally, suitable absorbent cores may contain reduced amounts ofcellulosic airfelt material. For instance, such cores may comprise lessthan about 40%, 30%, 20%, 10%, 5%, or even about 1%. Such a corecomprises primarily absorbent gelling material in amounts of at leastabout 60%, 70%, 80%, 85%, 90%, 95% or even about 100%, where theremainder of the core comprises a microfiber glue (if applicable). Suchcores, microfiber glues, and absorbent gelling materials are describedin U.S. Pat. Nos. 5,599,335; 5,562,646; 5,669,894; 6,790,798; and U.S.Patent Publications 2004/0158212A1 and 2004/0097895A1; and U.S.application Ser. Nos. 10/758,375 and 10/758,138, both filed on Jan. 15,2004.

In further embodiments, the articles of the present invention mayfurther comprise a wetness sensation member. This member may be disposedin various locations within the article. For instance, the wetnesssensation member may be disposed on the topsheet. The member maycomprise a permeable layer and an impermeable layer, wherein urinepasses through the permeable layer and not through the impermeable layersuch that a wearer is made aware of the fact that urination has occurredas a result of the “wet” feeling. Suitable members are detailed in U.S.Pat. No. 6,627,786.

An absorbent article according to the present invention may comprise arelatively narrow crotch width, which may increase the wearing comfort.An absorbent article of the present invention may comprise a crotchwidth of less than about 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or even lessthan about 50 mm. Hence, an absorbent core according to the presentinvention may have a crotch width as measured along a transversal linewhich is positioned at equal distance to the front edge and the rearedge of the core which may be less than about 100 mm, 90 mm, 80 mm, 70mm, 60 mm or even less than about 50 mm. It has been found that for mostabsorbent articles the liquid discharge occurs predominately in thefront half. The front half of the absorbent core should thereforecomprise most of the absorbent capacity of the core. The front half ofsaid absorbent core may comprise more than about 60% of the absorbentcapacity, or more than about 65%, 70%, 75%, 80%, 85%, or 90%.

These materials may be combined to provide an absorbent core in the formof one or more layers that may include fluid handling layers such as anacquisition layer, such as described in published WO 98/22279;distribution layer, such as one comprising chemically stiffened,modified or cross-linked cellulosic fibers; and storage layers such asone comprising superabsorbent polymers. The absorbent core may alsoinclude layers that may stabilize other core components. Such layersinclude a core cover, that may overlie a storage layer and underlie anyother core components if such components are present, and a dustinglayer, that may underlie a storage layer. Suitable materials for suchlayers may include spunbond/meltblown/spunbond nonwovens having a basisweight between about 10 and about 15 g/m² (the meltblown comprises lessthan about 5 g/m²). The fibrous structure described herein is alsosuitable for use in such layers.

The acquisition layer, distribution layer, storage layer, core cover,and dusting layer may generally be known as wrap sheets. Nonwoven wrapsheets may be fibrous structures, such as the fibrous structuredescribed herein, which may have the primary functionality of containingmaterials of the absorbent core therein without detrimentally impactingon the fluid handling properties of the absorbent core, even forsubsequent gushes. The containment functionality may be achieved byfibrous structures having small mean pore sizes, such as less than 30 μmwhen measured by the Coulter Porometer Mean Flow Pore size and Pore sizedistribution test in accordance with ASTM Test Method F316-86.

The wrap sheets may be permeable to aqueous liquids, such as by beingporous like fibrous webs or perforated film materials. The wrap sheetmay completely envelope the absorbent core. Alternatively, the wrapsheet need not completely envelope the absorbent core. The wrap sheetmay cover the top surface of the absorbent core and may then be tackeddown next to the core, such that the side surface may be, but notnecessarily have to be, covered by the wrap sheet. In yet anotherembodiment, the wrap sheet may cover the top surface of the absorbentcore as well as two side surfaces by being folded around these surfacesto partly or fully cover the bottom surface.

The wrapping of the absorbent core can also be achieved by more than onewrap sheet, or by one wrap sheet with different properties in differentregions thereof. For example, the surface parts of the absorbent corewhich are not in the fluid flow path, can have not, or non-permanentfluid hydrophilicity. Or, a different wrap material can be used in suchregions, or the absorbent core materials can there be contained by otherelements such as conventional tissue materials, but also impermeablesheets, which may at the same time have other functionalities.

Notably, hydrophilic fibrous structures are also useful in other partsof an absorbent article. For example, topsheets and acquisition layerscomprising hydrophilic fibrous structures as described above have beenfound to work well.

The liquid strike through time is a measure of a certain hydrophilicitylevel of fibrous structures. The value may be measured using the testmethod described herein.

Hydrophilizing Agent

FIG. 1 is illustrative, but by no means limiting, of an artist'sconception at the molecular level of a hydrophilizing agent 1 having adimeric “backbone,” a complementary segment 3, and hydrophilicsubstituents 4 associated with a complementary segment of a syntheticfiber 2, wherein n may be from about 1 to about 15.

While not intending to be limited by theory, it is surmised that thehydrophilizing agent becomes associated with one or more surfaces of thehydrophobic synthetic fiber. The association between the hydrophilizingagent and the synthetic fiber may be a durable association. Theassociation of the hydrophilizing agent with the synthetic fibers mayprovide for the synthetic fibers to exhibit hydrophilic characteristicsas opposed to the hydrophobic characteristics displayed by the syntheticfibers alone. It is further surmised that the hydrophobicity ofsynthetic fibers alone may generally cause the synthetic fibers to clumptogether during the webmaking process or within a fibrous structure.Whatever the reason, it has now been found that the association of ahydrophilizing agent with the synthetic fibers may provide for thedispersion of the synthetic fibers in a fibrous structure. For example,during a wet laid papermaking process, there may be a dispersion of thesynthetic fibers in a fluid carrier which may then promote thedispersion of the synthetic fibers in the fibrous structure. Naturalfibers may optionally be present in the dispersion as the natural fibersmay not interfere with the association of the hydrophilizing agent tothe synthetic fibers. The hydrophilizing agent may associate with thenatural fibers; however, this association will not prevent thehydrophilizing agent from associating with the synthetic fibers.

Hydrophilizing agents can include a variety of charged anionic orcationic species as well as noncharged monomer units. The anionic andcationic polymers may enhance both the deposition and the wettability ofthe synthetic fibers. Hydrophilizing agents comprising cationicfunctionalities are disclosed in U.S. Pat. No. 4,956,447. The structureof the hydrophilizing agents may be linear, branched or evenstar-shaped. Structures and charge distributions may be tailored forapplication to different fiber or textile types.

The hydrophilizing agent may associate with the synthetic fibers by acorrespondence between the hydrophilizing agent and the surfacecharacteristics of the synthetic fibers. This correspondence may bebased on physical characteristics of the synthetic fibers andhydrophilizing agent. Such physical characteristics may include, but arenot limited to, degree of crystallinity and molecular weight.Correspondence between the physical characteristics of thehydrophilizing agents and the synthetic fibers may aid in the durabilityof the association formed between the hydrophilizing agents and thesynthetic fibers. It has been found that an association based uponphysical characteristics may be durable wherein the hydrophilizing agentmay not wash off from the synthetic fibers. As such, the hydrophilizingagents of the present invention may be distinguished from typicalsurfactants. The bond between the synthetic fibers and thehydrophilizing agent may be durable. The synthetic fibers may exhibit adurable wettability. The synthetic fibers may exhibit a mean contactangle of less than about 72°. The synthetic fibers may exhibit a meancontact angle of less than about 72° and after a 10 minute water washthe mean contact angle of the synthetic fibers may remain below about72°. The synthetic fibers may exhibit a mean contact angle following a10 minute water wash of less than about 66°, 63°, 60°, 55° or 50°. Thesynthetic fibers exhibiting such mean contact angles may be associatedwith a hydrophilizing agent. The bond between the synthetic fibers andthe hydrophilizing agent may be durable and the hydrophilizing agent maynot be washed off the synthetic fibers after a single insult of fluid. Asurfactant, on the other hand, is unable to form such a durable bond andmay be washed off the synthetic fibers upon a single insult of fluid.Furthermore, a fibrous structure comprising synthetic fibers and ahydrophilizing agent may demonstrate a sustainable wettability, asdetailed herein, whereas a fibrous structure comprising synthetic fibersand a surfactant may not exhibit a sustainable wettability. A morepermanent association may be made between the hydrophilizing agent andthe synthetic fibers by heating the combination of the hydrophilizingagent and the synthetic fibers above the melting temperature of thehydrophilizing agent.

Hydrophilizing agents may comprise greater than about 3 ppm of ahydrophilizing agent/synthetic fiber and/or natural fiber combination.Hydrophilizing agents may generally comprise from about 10, 20, 30 or 40ppm to about 50, 60, 80 or 100 ppm of a hydrophilizing agent/syntheticfiber and/or natural fibers combination. The compositions herein maycomprise greater than about 0.001% of a hydrophilizing agent. Thecompositions herein may comprise from about 0.001% to about 2%, 5%, 10%or 20% of a hydrophilizing agent.

The hydrophilizing agent may comprise a segment that may becomplementary to the polymer of the synthetic fibers. The complementarysegment may comprise a polyester segment. The polyester segment maycomprise a polyethylene terephthalate segment. The hydrophilizing agentmay be oligomeric or polymeric. The hydrophilizing agent may be acopolymer of ethoxylate siloxane. The hydrophilizing agent may be soilrelease agent. Such a hydrophilizing agent may be a polymer. Polymerichydrophilizing agents useful in the present invention may include, butare not limited to materials selected from the group consisting ofpolyester, poly(ethoxylate), polyethylene oxide, polyoxyethylene,polyethylene glycol, polypropylene glycol, terephthalate, polypropyleneoxide, polyethylene terephthalate, polyoxyethylene terephthalate,ethoxylate siloxane and combinations thereof. Polyesters of terephthalicand other aromatic dicarboxylic acids having soil release propertiessuch as polyethylene terephthalate/polyoxyethylene terephthalate andpolyethylene terephthalate/polyethylene glycol polymers, among otherpolyester polymers, may be utilized as the hydrophilizing agent in thefibrous structure. As noted above, a wide variety of hydrophilizingagents, also known as SRP's, SRA's, and SRE's, are well-recognizedmaterials in the detergency arts, and many are available commercially orby synthesis schemes disclosed in multiple patents of The Procter &Gamble Company and various manufacturers.

Higher molecular weight (e.g., 40,000 to 50,000 M.W.) polyesterscontaining random or block ethylene terephthalate/polyethylene glycol(PEG) terephthalate units have been used as soil release agents inlaundry cleaning compositions. See U.S. Pat. Nos. 3,893,929; 3,959,230;and 3,962,152. Sulfonated linear terephthalate ester oligomers aredisclosed in U.S. Pat. No. 4,968,451. Nonionic end-capped1,2-propylene/polyoxyethylene terephthalate polyesters are disclosed inU.S. Pat. No. 4,711,730 and nonionic-capped block polyester oligomericcompounds are disclosed in U.S. Pat. No. 4,702,857. Partly- andfully-anionic-end-capped oligomeric esters are disclosed further in U.S.Pat. No. 4,721,580 and anionic, especially sulfoaroyl, end-cappedterephthalate esters are disclosed in U.S. Pat. No. 4,877,896 and U.S.Pat. No. 5,415,807.

U.S. Pat. No. 4,427,557 discloses low molecular weight copolyesters(M.W. 2,000 to 10,000) which can be used in aqueous dispersions toimpart soil release properties to polyester fibers. The copolyesters areformed by the reaction of ethylene glycol, a PEG having an averagemolecular weight of 200 to 1000, an aromatic dicarboxylic acid (e.g.,dimethyl terephthalate), and a sulfonated aromatic dicarboxylic acid(e.g., dimethyl 5-sulfoisophthalate). The PEG can be replaced in partwith monoalkylethers of PEG such as the methyl, ethyl and butyl ethers.

A hydrophilizing agent may be a copolymer having blocks of terephthalateand polyethylene oxide. More specifically, these polymers may compriserepeating units of ethylene and/or propylene terephthalate andpolyethylene oxide terephthalate at a molar ratio of ethyleneterephthalate units to polyethylene oxide terephthalate units of fromabout 25:75 to about 35:65, said polyethylene oxide terephthalatecontaining polyethylene oxide blocks having molecular weights of fromabout 300 to about 2000. The molecular weight of this polymerichydrophilizing agent may be in the range of from about 5,000 to about55,000.

Another polymeric hydrophilizing agent may be a crystallizable polyesterwith repeat units of ethylene terephthalate units comprising from about10% to about 15% by weight of ethylene terephthalate units together withfrom about 10% to about 50% by weight of polyoxyethylene terephthalateunits, derived from a polyoxyethylene glycol of average molecular weightof from about 300 to about 6,000, and the molar ratio of ethyleneterephthalate units to polyoxyethylene terephthalate units in thecrystallizable polymeric compound may be between 2:1 and 6:1. Examplesof this polymer include the commercially available materials ZELCON®4780 (from DuPont) and MILEASE® T (from ICI).

In another embodiment, the poly(ethoxylate) regions may be tailored tohave from about 1 to about 9, 12, or 15 ethoxylated groups and any othernumber of ethoxylated groups within the range of from about 1 to about15. The number of poly(ethoxylated) regions may be tailored to enhancethe wettability of the synthetic fibers. Wettability of the syntheticfibers may be increased as the number of ethoxylated groups increases inthe poly(ethoxylate) regions. Optionally, additional copolymers such as,but not limited to, polyethylene glycol and polypropylene glycol, may beused to control the crystallinity of the hydrophilizing agents.

In an alternative embodiment, the hydrophilizing agents provided by theinvention may be illustrated by one comprising from about 25% to about100% by weight of an ester having the empirical formula(CAP)_(x)(EG/PG)_(y′)(DEG)_(y″),(PEG)_(y′″)(T)_(z)(SIP)_(q); wherein(CAP) represents the sodium salt form of said end-capping units i);(EG/PG) represents said oxyethyleneoxy and oxy-1,2-propyleneoxy unitsii); (DEG) represents said di(oxyethylene)oxy units iii); (PEG)represents said poly(oxyethylene)oxy units iv); (T) represents saidterephthaloyl units v); (SIP) represents the sodium salt form of5-sulfoisophthaloyl units vi); x is from about 1 to 2; y′ is from about0.5 to about 66; y″ is from 0 to about 50; y′″ is from 0 to about 50;y′+y″+y′″ totals from about 0.5 to about 66; z is from about 1.5 toabout 40; and q is from about 0.05 to about 26; wherein x, y′, y″, y′″,z and q represent the average number of moles of the corresponding unitsper mole of said ester. Hydrophilizing agents may be those wherein atleast about 50% by weight of said ester has a molecular weight rangingfrom about 500 to about 5,000.

In one embodiment, the hydrophilizing agents may haveoxyethyleneoxy:oxy-1,2-propyleneoxy mole ratio ranges from about 0.5:1to about 10:1; x is about 2, y′ is from about 2 to about 27, z is fromabout 2 to about 20, and q is about 0.4 to about 8. In anotherembodiment, x is about 2, y′ is about 5, z is about 5, and q is about 1.

The hydrophilizing agents may associate with the synthetic fiber surfaceduring the process of re-pulping the fibers. The synthetic fibers mayalso be provided with a finishing coat of the hydrophilizing agent priorto re-pulping the fibers. Additionally, the hydrophilizing agent mayassociate with the synthetic fibers as a melt-additive prior toextrusion of the synthetic fibers.

Additional information relating to hydrophilizing agents may be found inU.S. Pat. Nos. 4,702,857; 4,861,512; 5,574,179 and 5,843,878.

Method of Making Fibrous Structure

Generally, the process of the present invention for making a unitaryfibrous structure may be described in terms of forming a web having aplurality of synthetic fibers disposed in a generally random patternthroughout the fibrous structure. A plurality of natural fibers may alsobe disposed in a generally random pattern throughout the fibrousstructure. In another embodiment, a portion of the synthetic fibers maybe redistributed in a non-random repeating pattern. Layered depositionof the fibers, synthetic and natural, is also contemplated by thepresent invention.

In a typical wet-laid process, the plurality of fibers may be suspendedin a fluid carrier. This may also be known as “re-pulping” the fibers.Synthetic fibers may be re-pulped separately from or in combination withnatural fibers. In another embodiment, a plurality of synthetic fibersand a plurality of natural fibers may both be added to a re-pulper. Ahydrophilizing agent may then be added to the re-pulper to associatewith the synthetic fibers. In yet another embodiment, a plurality ofsynthetic fibers may be added to a re-pulper and mixed with ahydrophilizing agent. This combination may then be mixed with aplurality of natural fibers. As an alternative, the synthetic fibers mayassociate with a hydrophilizing agent by providing the synthetic fiberswith a finishing coat containing a hydrophilizing agent prior to beingre-pulped. The synthetic fibers may then be re-pulped and combined withnatural fibers. Alternatively, the hydrophilizing agent may associatewith the synthetic fibers as a melt-additive prior to extrusion of thefibers.

In yet another embodiment, the process may be air-laid in which aplurality of synthetic fibers associated with a hydrophilizing agent areplaced directly into the papermaking machinery. In such an embodiment, aplurality of natural fibers may also be placed directly into thepapermaking machinery. In addition to wet-laid and air-laid, othermethods may include, but are not limited to, melt-blown, spun-bond,carded, co-form, adhesive bonding, needle punched, hydroentangled,lamination or other processes known in the art for such purposes.Combinations of the methods can also be used.

The resulting fibrous structure may comprise natural and syntheticfibers dispersed generally randomly throughout the layer. Alternatively,the natural and synthetic fibers may be more structured such that thesynthetic fibers and natural fibers may be disposed generallynon-randomly. In one embodiment, the fibrous structure may include atleast one layer comprising a plurality of natural fibers and at leastone adjacent layer comprising a plurality of synthetic fibers. Inanother embodiment, the fibrous structure may include at least one layerthat comprises a plurality of synthetic fibers homogeneously mixed withnatural fibers and at least one adjacent layer that comprises aplurality of natural fibers. In an alternate embodiment, the fibrousstructure may include at least one layer that comprises a plurality ofnatural fibers and at least one adjacent layer that comprises a mixtureof a plurality of synthetic fibers and a plurality of natural fibers inwhich the synthetic fibers and/or natural fibers may be disposedgenerally non-randomly. Further, one or more of the layers of mixednatural fibers and synthetic fibers may be redistributed in apredetermined pattern or other non-random pattern.

FIG. 7 schematically shows one embodiment of the fibrous structure 100wherein the natural fibers 110 are randomly distributed throughout thestructure, and the synthetic fibers 120 are redistributed in anon-random repeating pattern. FIG. 8 illustrates a fibrous structure 100that may comprise a plurality of natural fibers 110 and a plurality ofsynthetic fibers 120 randomly distributed throughout the fibrousstructure.

The following illustrates the practice of the invention, but is notintended to be limiting thereof.

Example 1

Four different handsheets using Northern Softwood Kraft and CoPET/PET(isophthalic acid copolymers) fibers with or without differenthydrophilizing agents are prepared and tested for their impact onHorizontal Absorptive Capacity (H.A.C.) as determined by the HorizontalFull Sheet (HFS) test method described below.

All values below are an average of four separate handsheets.

As shown in the following Table, synthetic fiber addition has a negativeimpact (˜8% loss) on Horizontal Absorptive Capacity (H.A.C.). Additionof hydrophilizing agents makes the synthetic fibers hydrophilic enoughto recover the loss in absorptive capacity.

Basis Weight, g/m² H.A.C. g/g H.A.C. Ratio Sample A (Base) 26.7 11.551.00 Sample B 28.3 10.60 0.92 Sample C 27.2 11.77 1.02 Sample D 27.611.68 1.01 Sample A 100% Northern Softwood Kraft (Control sample withcellulosic fibers only) Sample B About 70% Northern Softwood Kraft andabout 30% CoPET/PET Sample C About 70% Northern Softwood Kraft and about30% CoPET/PET and about 40 ppm TexCare ™ SRN-240 Sample D About 70%Northern Softwood Kraft and about 30% CoPET/PET and about 50 ppmTexCare ™ SRN-100

CoPET/PET fibers are commercially available from Fiber InnovationTechnology, Inc., Johnson City, Tenn. The CoPET/PET fibers as used inthis example are designated as T-235 by Fiber Innovation Technology.TexCare SRN-100 and TexCare SRN-240 are commercially available fromClairant GmBH, Division Functional Chemicals, Frankfurt am Main.

H.A.C. Ratio=H.A.C. of the Sample/H.A.C. of the Base Sample A

For this Example, the HFS procedure is modified. Four inch (10.2 cm) by4 inch (10.2 cm) paper samples are used rather than 11 inch (27.9 cm) by11 inch (27.9 cm) samples as described in the procedure.

Example 2

A pilot scale Fourdrinier papermaking machine is used in the presentexample. A 3%, by weight, aqueous slurry of Northern Softwood Kraft(NSK) is made up in a conventional re-pulper. The NSK slurry is refinedgently and a 2% solution of a permanent wet strength resin (i.e., Kymene557LX which is marketed by Hercules Inc., Wilmington, Del.) is added tothe NSK stock pipe at a rate of 1%, by weight of the dry fibers. Theadsorption of Kymene 557LX to NSK is enhanced by an in-line mixer. A 1%solution of Carboxy Methyl Cellulose (CMC) is added after the in-linemixer at a rate of 0.2%, by weight of the dry fibers, to enhance the drystrength of the fibrous substrate. A 3%, by weight, aqueous slurry ofEucalyptus fibers is made up in a conventional re-pulper.

The NSK slurry and the Eucalyptus fibers are layered in a head box anddeposited onto a Fourdrinier wire as different layers to form anembryonic web. Dewatering occurs through the Foudrinier wire and isassisted by a deflector and vacuum boxes. The Fourdrinier wire is of a5-shed, satin weave configuration having 84 machine-direction and 76cross-machine-direction monofilaments per inch, respectively. The wetembryonic web is transferred from the Fourdrinier wire, at a fiberconsistency of about 18% at the point of transfer, to a photo-polymerfabric having 150 Linear Idaho cells per square inch, 20 percent knuckleareas and 17 mils of photo-polymer depth. Further de-watering isaccomplished by vacuum assisted drainage until the web has a fiberconsistency of about 22%. The patterned web is pre-dried by airblow-through to a fiber consistency of about 56% by weight. The web isthen adhered to the surface of a Yankee dryer with a sprayed crepingadhesive comprising 0.25% aqueous solution of Polyvinyl Alcohol (PVA).The fiber consistency is increased to an estimated 96% before drycreping the web with a scalpel blade. The scalpel blade has a bevelangle of about 25 degrees and is positioned with respect to the Yankeedryer to provide an impact angle of about 81 degrees; the Yankee dryeris operated at about 600 fpm (feet per minute) (about 183 meters perminute). The dry web is formed into roll at a speed of 560 fpm (171meters per minutes).

Two plies of the web are formed into paper towel products by embossingand laminating them together using PVA adhesive. The paper towel hasabout 40 g/m² basis weight and contains 70% by weight Northern SoftwoodKraft and 30% by weight Eucalyptus furnish. The resulting paper towelhas an absorptive capacity of 26.3 gram/gram. The resulting paper towelmay also provide a Horizontal Rate Capacity (HRC) value, determinedaccording to the test method described herein. In this example, the HRCvalue is 0.57 g/sec.

Example 3

A paper towel is made by a method similar to that of Example 2, butreplacing 10% by weight of Eucalyptus by 10% by weight of 6 mm in lengthand about 20 microns in diameter synthetic bicomponent polyester fibers.The polyester fibers as used in this example are available from FiberInnovation Technology and are designated as T-201. Forty ppm TexCare™SRN-240 is added to the Eucalyptus-synthetic fiber pulp mixture. Thepaper towel has about 40 g/m² basis weight and contains 70% by weightNorthern Softwood Kraft in one layer and a mixture of 20% by weightEucalyptus and 10% by weight of the 6 mm long synthetic fibers in theother layer. The resulting paper towel has an absorptive capacity of26.3 gram/gram. The resulting HRC value for this paper towel is 0.56g/sec.

Example 4

A paper towel is made by a method similar to that of Example 2, butreplacing 5% by weight of Eucalyptus by 5% by weight of 6 mm syntheticbicomponent polyester fibers. The polyester fibers of this example areavailable from Fiber Innovation Technology and are designated as T-201.Forty ppm TexCare™ SRN-240 is added to the Eucalyptus-synthetic fiberpulp mixture. The paper towel has about 40 g/m² basis weight andcontains 70% by weight Northern Softwood Kraft in one layer and amixture of 25% by weight Eucalyptus and 5% by weight of the 6 mm longsynthetic fibers in the other layer. The resulting paper towel has anabsorptive capacity of 26.2 gram/gram. The resulting HRC value for thispaper towel is 0.57 g/sec.

Example 5

Two different handsheets using Northern Softwood Kraft and CoPET/PET(isophthalic acid copolymers) fibers with or without differenthydrophilizing agents are prepared and tested for their impact on LiquidHandling as determined by the Liquid Strike Through test methoddescribed below.

Strikethrough¹ (sec) Sample 1st, 3rd, 5th A 2.5, 3.5, 2.3 (±0.3, 0.5,0.2) B 1.4, 2.2, 1.8 (±0.2, 0.2, 0.2) ¹GCAS64011333, Lister Model 2005,SN L5877 Sample A About 30gsm, of about 20% CoPET/PET and about 80%Northern Softwood Kraft and about 40 ppm TexCare ™ SRN-240 Sample BAbout 17gsm, of about 73% Northern softwood Kraft and about 27%CoPET/PET and about 40 ppm TexCare ™ SRN-240

CoPET/PET fibers are commercially available from Fiber InnovationTechnology, Inc., Johnson City, Tenn. The CoPET/PET fibers as used inthis example are designated as T-201 by Fiber Innovation Technology.TexCare SRN-240 are commercially available from Clairant GmBH, DivisionFunctional Chemicals, Frankfurt am Main.

Example 6

A disposable article which is a training pant or a diaper as detailed inany one of U.S. Pat. Nos. 3,860,003; 4,632,207; 4,695,278; 4,704,115;4,795,454; 4,900,317; 4,909,803 (Reissued as USRE34920); U.S. Pat. Nos.5,085,654; 5,492,751; 6,476,288; 6,627,787; 5,507,760; 5,609,587;5,635,191; 5,643,588; 6,118,041 and SIR H1630 with the exception thatthe core has been replaced by the one described below. The core that isincluded in the article of this example consists of a polypropylenedusting layer (13 gsm) that measures about 140 mm×390 mm. The dustinglayer is slot coated longitudinally down the center 97 mm with asuitable adhesive, e.g., HB Fuller 1358 LO, at an add-on amount of about5 grams along the length. A superabsorbent material, e.g., BASF's ASAP600Z, is applied via a print roll to the slot coated dusting layer suchthat a profiled superabsorbent material pattern is deposited onto thedusting layer at an add-on amount of about 9.4 grams along the length ofthe dusting layer in the form of a rectangle that is 90 mm wide in eachof the 4 quarters of its length. A sufficient amount, e.g., of amicrofiber glue, e.g., Fuller's NW 1151ZP, is continually applied viaspraying onto the superabsorbent material for immobilization of thematerial. The material of any one of Examples 1-4 is cut to the samesize as the dusting layer and is slot coated with the same suitableadhesive HL 1358 LO and placed on top of the superabsorbent coateddusting layer. This pad forms the absorbent core that is then used inany one of the absorbent articles disclosed above.

Example 7

A disposable article which is a training pant or a diaper as detailed inany one of the patents listed in Example 6 with the exception that thecore has been replaced by the one described below. The core that isincluded in the article of this example consists of a polypropylenedusting layer (13 gsm) that measures about 140 mm×390 mm. The dustinglayer is slot coated longitudinally down the center 97 mm with asuitable adhesive, e.g., HB Fuller 1358 LO, at an add-on amount of about5 grams along the length. A layer of superabsorbent material is appliedvia a print roll to the slot coated dusting layer. A first layer ofsuperabsorbent material, e.g., BASF's ASAP 600Z, is applied such that aprofiled superabsorbent material pattern is deposited onto the dustinglayer at an add-on amount of about 2.2 grams along the length of thedusting layer in the form of a rectangle that is 90 mm wide in each ofthe 4 quarters of its length. A sufficient amount, e.g., of a microfiberglue, e.g., Fuller's NW 1151ZP, is intermittently applied via sprayingonto the superabsorbent material for immobilization of the material. Asecond layer of superabsorbent material, e.g., BASF's ASAP 600Z, isapplied to a piece of material such as described in any one of Examples1-4 that is the same size as the dusting layer. This material serves asa core cover and is slot coated with a suitable adhesive prior to thedeposition of the superabsorbent material. A profiled superabsorbentmaterial pattern is deposited onto the core cover at an add-on amount ofabout 6.8 grams along the length of the core cover in the form of arectangle that is 90 mm wide in each of the 4 quarters of its length. Atotal amount of superabsorbent material is about 9.0 grams. A sufficientamount, e.g., of a microfiber glue, e.g., Fuller's NW 1151ZP, iscontinuously applied via spraying onto the second layer ofsuperabsorbent material for immobilization of the material. This padforms the absorbent core that is then used in any one of the absorbentarticles disclosed above.

Example 8

A disposable article which is a training pant or a diaper as detailed inany one of the patents listed in Example 6 with the exception that thecore has been replaced by the one described below. The core that isincluded in the article of this example is 90 mm wide in the 1^(st) and4^(th) quarters and narrower in the 2^(nd) and 3^(rd) quarters, such as80 mm wide. The core that is included in the article of this exampleconsists of a polypropylene dusting layer (13 gsm) that measures about125 mm×390 mm. The dusting layer is slot coated longitudinally down thecenter 97 mm with a suitable adhesive, e.g., HB Fuller 1358 LO, at anadd-on amount of about 5 grams along the length. A layer ofsuperabsorbent material is applied via a print roll to the slot coateddusting layer. A first layer of superabsorbent material, e.g., BASF'sASAP 600Z, is applied such that a profiled superabsorbent materialpattern is deposited onto the dusting layer at an add-on amount of about3.2 grams along the length of the dusting layer. A sufficient amount,e.g., of a microfiber glue, e.g., Fuller's NW 1151ZP, is intermittentlyapplied via spraying onto the superabsorbent material for immobilizationof the material. A second layer of superabsorbent material, e.g., BASF'sASAP 600Z, is applied to a piece of material such as described in anyone of Examples 1-4 that is the same size as the Dusting Layer. Aprofiled superabsorbent material pattern is deposited onto the corecover at an add-on amount of about 9.3 grams along the length of thecore cover. A total amount of superabsorbent material is about 12.5grams. A sufficient amount, e.g., of a microfiber glue, e.g., Fuller'sNW 1151ZP, is continuously applied via spraying onto the second layer ofsuperabsorbent material for immobilization of the material. This padforms the absorbent core that is then used in any one of the absorbentarticles disclosed above.

Horizontal Full Sheet (HFS) Test Method

The Horizontal Full Sheet (HFS) test method determines the amount ofdistilled water absorbed and retained by the fibrous structure of thepresent invention. This method is performed by first weighing a sampleof the fibrous structure to be tested (referred to herein as the “dryweight of the sample”), then thoroughly wetting the sample, draining thewetted sample in a horizontal position and then reweighing (referred toherein as “wet weight of the sample”). The absorptive capacity of thesample is then computed as the amount of water retained in units ofgrams of water absorbed by the sample. When evaluating different fibrousstructure samples, the same size of fibrous structure is used for allsamples tested.

The apparatus for determining the HFS capacity of fibrous structurescomprises the following:

1) An electronic balance with a sensitivity of at least ±0.01 grams anda minimum capacity of 1200 grams. The balance should be positioned on abalance table and slab to minimize the vibration effects offloor/benchtop weighing. The balance should also have a special balancepan to be able to handle the size of the sample tested (i.e.; a fibrousstructure sample of about 11 in. (27.9 cm) by 11 in. (27.9 cm)). Thebalance pan can be made out of a variety of materials. Plexiglass is acommon material used.2) A sample support rack and sample support cover is also required. Boththe rack and cover are comprised of a lightweight metal frame, strungwith 0.012 in. (0.305 cm) diameter monofilament so as to form a grid of0.5 inch squares (1.27 cm²). The size of the support rack and cover issuch that the sample size can be conveniently placed between the two.

The HFS test is performed in an environment maintained at 23±1° C. and50±2% relative humidity. A water reservoir or tub is filled withdistilled water at 23±1° C. to a depth of 3 inches (7.6 cm).

The fibrous structure sample to be tested is carefully weighed on thebalance to the nearest 0.01 grams. The dry weight of the sample isreported to the nearest 0.01 grams. The empty sample support rack isplaced on the balance with the special balance pan described above. Thebalance is then zeroed (tared). The sample is carefully placed on thesample support rack. The support rack cover is placed on top of thesupport rack. The sample (now sandwiched between the rack and cover) issubmerged in the water reservoir. After the sample is submerged for 60seconds, the sample support rack and cover are gently raised out of thereservoir.

The sample, support rack and cover are allowed to drain horizontally for120±5 seconds, taking care not to excessively shake or vibrate thesample. While the sample is draining, the rack cover is carefullyremoved and all excess water is wiped from the support rack. The wetsample and the support rack are weighed on the previously tared balance.The weight is recorded to the nearest 0.01 g. This is the wet weight ofthe sample.

The gram per fibrous structure sample absorptive capacity of the sampleis defined as (wet weight of the sample−dry weight of the sample). Thehorizontal absorbent capacity is defined as: absorbent capacity=(wetweight of the sample−dry weight of the sample)/(dry weight of thesample) and has a unit of gram/gram.

Horizontal Rate Capacity (HRC) Method

Horizontal Rate Capacity (HRC) is an absorbency rate test that measuresthe quantity of water taken up by a paper sample in a two second timeperiod. The value is reported in grams of water per second. Theinstrument used to carry out the HRC measurement comprises a pump,pressure gauge, inlet shunt, rotometer, reservoir, sump, outlet shunt,water supply tube, sample holder, sample, balance, and tubing. Theinstrument is illustrated in U.S. Pat. No. 5,908,707 issued to Cabell etal. the disclosure of which is incorporated herein by reference for thepurposes of showing the instrument used to carry out the HRCmeasurement.

In this method, the sample (cut using a 3 in. (7.6 cm) diameter cuttingdie) is placed horizontally in a holder suspended from an electronicbalance. The holder is made up of a lightweight frame measuringapproximately 7 in. by 7 in. (17 cm by 17 cm), with lightweight nylonmonofilament strung through the frame to form a grid of 0.5 in. (1.27cm) squares. The nylon monofilament for stringing the support rackshould be 0.069.±0.005 in. (0.175 cm.±0.0127 cm) in diameter (e.g.,Berkley Trilene Line 2 lb test clear). The electronic balance usedshould be capable of measuring to the nearest 0.001 g. (e.g., SartoriousL420P+).

The sample in the holder is centered above a water supply tube. Thewater supply is a plastic tube having a 0.312 inch (0.79 cm) insidediameter containing distilled water at 23°±1° C. The supply tube isconnected to a fluid reservoir at zero hydrostatic head relative to thetest sample. The water supply tube is connected to the reservoir usingplastic (e.g. Tygon®) tubing. The height of the nylon monofilament ofthe sample holder is located 0.125 in ±1/64 in. (0.32 cm±0.04 cm) abovethe top of the water supply tube.

The water height in the reservoir should be level with the top of thewater supply tube. The water in the reservoir is continuously circulatedusing a water pump circulation rate of 85-93 ml/second using a waterpump (e.g., Cole-Palmer Masterflex 7518-02) with #6409-15 plastictubing. The circulation rate is measured by a rotometer tube (e.g.,Cole-Palmer N092-04 having stainless steel valves and float). Thiscirculation rate through the rotometer creates a head pressure of2.5±0.5 psi as measured by an Ashcroft glycerine filled gauge.

Before conducting this measurement, the samples should be conditioned to23°±1° C. and 50±2% Relative Humidity for 2 hours. The HRC test is alsoperformed in these controlled environmental conditions.

To start the absorbent rate measurement, the 3 in. (7.62 cm) sample isplaced on the sample holder. Its weight is recorded in 1 secondintervals for a total of 5 seconds. The weight is averaged (hereinreferred to as “Average Sample Dry Weight”). Next, the circulating wateris shunted to the sample water supply for 0.5 seconds by shuntingthrough the valve. The weight reading on the electronic balance ismonitored. When the weight begins to increase from zero a stop watch isstarted. At 2.0 seconds the sample water supply is shunted to the inletof the circulating pump to break contact between the sample and thewater in the supply tube.

The shunt is performed by diverting through the valve. The minimum shunttime is at least 5 seconds. The weight of the sample and absorbed wateris recorded to the nearest 0.001 g. at time equals 11.0, 12.0, 13.0,14.0 and 15.0 seconds. The five measurements are averaged and recordedas “Average Sample Wet Weight”.

The increase in weight of the sample as a result of water being absorbedfrom the tube to the sample is used to determine the absorbency rate. Inthis case, the rate (grams of water per second) is calculated as:

(Average Sample Wet Weight−Average Sample Dry Weight)/2 seconds

It is understood by one skilled in the art that the timing, pulsingsequences, and electronic weight measurement can be computer automated.

Liquid Strike-Through Test

The liquid strike-through time is measured using Lister-typestrike-through equipment, manufactured by Lenzing AG, Austria. Testprocedure is based on standardized WSP (World Strategic Partners)70.7(05), with the test sample placed on an absorbent pad comprised often plies of filter paper (Ahlstrom Grade 989 obtained from EmpiricalManufacturing Co., Inc., or equivalent). In a typical experiment, threeconsecutive 5 ml gushes of test liquid (0.9% saline solution) areapplied to a non-woven sample at one minute intervals and the respectivestrike-through times are recorded without changing the absorbent pad.

In addition to measuring the strike-through time for the first gush, asdescribed in the WSP Method, the test described below does not onlymeasure the first gush but several subsequent gushes, especially thefifth gush.

Apparatus—Lister Strike-through Equipment—(i) A Funnel fitted withmagnetic valve: Rate of discharge of 25 ml in 3.5 (±0.25) seconds; (ii)A Strike-through plate: Constructed of 25 mm thick acrylic glass. Thetotal weight of the plate must be 500 g. The electrodes should be ofnon-corrosive material. The electrodes are set in (4.0 mm×7.0 mm) crosssection grooves, cut in the base of the plate and fixed with quicksetting epoxy resin. FIGS. 6, 7, and 8 illustrate a Strike-through plate200 containing electrodes 210. FIG. 6 is a top view of a Strike-throughplate 200, whereas FIG. 7 is a sectional view along 9-9 of theStrike-through plate 200 of FIG. 6. FIG. 8 is a sectional perspectiveview along 10-10 of the Strike-through plate 200 of FIG. 6; (iii) Baseplate: A square of acrylic glass 125 mm×125 mm approximately; (iv) Ringstand to support the funnel; (v) Electronic Timer measuring to 0.01seconds; (vi) Burette with SO ml capacity; and (vii) Core filter paperAhlstrom Grade 989 or equivalent (average Strike-through time 1.7 s+−0.3s, dimensions: 10×10 cm).

Procedure: (1) Carefully cut the required number of samples, 12.5cm×12.5 cm with touching the sample only at the edge of the sample. (2)Taking 10 plies of Core filter paper place one sample on the set of 10plies of filter paper on the base plate. The sample should be positionedon the filter paper in such a way that the side of the nonwoven, whichis intended to face the user's skin, (when applied in an absorbentarticle) is uppermost. (3) Place the strike through plate on top withthe center of the plate over the center of the test piece. Center theburette and the funnel over the plate. (4) Ensuring that the electrodesare connected to the timer, switch on the timer and set the clock tozero. (5) Fill the burette with saline solution (0.9 wt % NaCl indeionized water). (6) Keep the discharge valve of the funnel closed andrun 5.0 ml of liquid (=one gush) from the burette into the funnel (7)Open the magnetic valve of the funnel to discharge 5.0 ml of liquid. Theinitial flow of liquid will complete the electrical circuit and startthe timer. It will stop when the liquid has penetrated into the pad andfallen below the level of the electrodes in the strike through plate.(8) Record the time indicated on the electronic timer. (9) Wait 60seconds and repeat steps (4) and (6) to (9) for the second, third andany subsequent gush, with each gush comprising 5 ml of liquid. (e.g., 5ml into funnel, open magnetic valve, etc.) Record the time for the1^(st), 2^(nd), and any subsequent gush in seconds.

Method of Detection of Association of Hydrophilizing Agent and SyntheticFibers

A nonwoven fibrous structure may be analyzed for the association ofsynthetic fibers and a hydrophilizing agent in a variety of ways. Thefibrous structure may be separated into its component parts which mayinclude synthetic fibers and natural fibers. The synthetic fibers andnatural fibers may be separated from each other by any suitable methodknown to one of ordinary skill in the art.

A method of analyzing the association of synthetic fibers andhydrophilizing agent may include the utilization of the Wilhelmy balancetechnique. In such a method, the analysis is performed by mounting anindividual fiber, such as a synthetic fiber separated from the fibrousstructure as discussed above, vertically and measuring the force ofwater as a function of position as the fiber dips into the water. Thecontact angle is calculated from the regressed force data and fiberdiameter. As an example of such a method, the following table mayillustrate the mean contact angle for fibers taken from two handsheets.The numbers presented are an average of three fibers of each sample typein triplicate. The mean contact angle for the two fibers types isstatistically different and may indicate that a hydrophilizing agent hasassociated with the synthetic fibers of Sample B and has therefore madethe fibers more hydrophilic than those of Sample A.

Fiber Mean Standard Diameter (μm) Contact Angle Deviation Sample A 14.3673.4° 2.4° Sample B 15.04 56.4 2.8 Sample A: About 70% Northern SoftwoodKraft cellulose fibers and about 30% CoPET/PET fibers. Sample B: About70% Northern Softwood Kraft cellulose fibers and about 30% CoPET/PETfibers and about 40 ppm TexCare ™ SRN-240.

Another method for analyzing the association of synthetic fibers andhydrophilizing agent may include the separation of the fibers asdescribed. The synthetic fibers may then undergo an extraction process,such as a solvent extraction, to remove any surface coatings, elements,contaminants, etc from the synthetic fibers to result in “clean”synthetic fibers. The solvent extract may be analyzed by any suitablemethod known to one of ordinary skill, including, but not limited to,liquid chromatography, mass spectrometry, static time-of-flightsecondary ion mass spectrometry, etc. to determine the presence of ahydrophilizing agent, such as a hydrophilizing agent comprising apolyester segment. The synthetic fibers and the hydrophilzing agent maybe analyzed to determine the actual synthetic fiber and the actualhydrophilizing agent present in the fibrous structure. The presence ofboth synthetic fibers and hydrophilizing agent characterizes theassociation of the synthetic fibers with the hydrophilizing agent.

Method of Determining Durability of Association of Hydrophilizing Agentand Synthetic Fibers

Synthetic fibers may be analyzed for the durability of the associationof the synthetic fibers and a hydrophilizing agent. A method fordetermining the durability of the association may relate to thewettability of the synthetic fibers. Contact angle measurement of aliquid, such as water, in contact with the synthetic fibers may providefor a determination of the durability of the association between asynthetic fiber and a hydrophilizing agent. A wettable synthetic fibermay demonstrate the association of the synthetic fiber and ahydrophilizing agent. A demonstration of the wettability of thesynthetic fiber following multiple washings may demonstrate thedurability of the association of the synthetic fiber and ahydrophilizing agent.

The synthetic fibers may be dried at about 80° C. in an air flow ovenfor about 24 hours. The synthetic fibers may be placed in a beaker andwashed in warm water (about 60° C.) for two hours with gentle stirringto remove any residual process aids. The ratio of fibers to water volumemay be about 1:200. After washing, the fibers may be collected and driedovernight at room temperature. The synthetic fibers may be separatedinto four groups, with each group weighing about 36 grams, and placed inan air flow over for about 10 hour. Four aliquots, each about 5 grams,may be separated out and may be treated with a hydrophilizing agent anda surfactant at two varying levels, such as 40 ppm and 400 ppm.Therefore, one aliquot of 5 grams of synthetic fibers may be soaked inabout 40 ppm of a hydrophilizing agent for about 10 minutes. A secondaliquot of 5 grams of synthetic fibers may be soaked in about 400 ppm ofa hydrophilizing agent for about 10 minutes. A third aliquot of about 5grams of synthetic fibers may be soaked in about 40 ppm of a surfactantfor about 10 minutes. A fourth aliquot of 5 grams of synthetic fibersmay be soaked in about 400 ppm of a surfactant for about 10 minutes. Theratio of each treatment group of synthetic fibers to treatment is 5 g:100 ml of solution. The four groups of synthetic fibers may be driedpost-treatment at room temperature. After drying, the four groups ofsynthetic fibers may be subjected to about 10 minutes of water washingusing double distilled water at about 45° C.

A method of analyzing the association of synthetic fibers andhydrophilizing agent or surfactant may include the utilization of theWilhelmy balance technique. In such a method, the analysis is performedby mounting an individual fiber vertically and measuring the force ofwater as a function of position as the fiber dips into the water. Thecontact angle is calculated from the regressed force data and fiberdiameter. As an example of such a method, the following table mayillustrate the mean contact angle for synthetic fibers that have beensubjected to the above various treatments and wash steps. The numberspresented are an average of two fibers of each sample type intriplicate.

Mean Contact Standard Fiber Angle Deviation Diameter Sample TreatmentWater Wash (°) (°) (μm) 1 40 ppm None 54.9 1.8 13.40 HydrophilizingAgent 2 400 ppm None 52.2 1.7 15.14 Hydrophilizing Agent 3 40 ppm None71.3 1.9 14.06 Surfactant 4 400 ppm None 60.9 2.3 14.78 Surfactant 5 40ppm 10 Minutes 62.2 1.9 13.45 Hydrophilizing Agent 6 400 ppm 10 Minutes66.1 1.8 15.13 Hydrophilizing Agent 7 40 ppm 10 Minutes 80.0 2.1 14.78Surfactant 8 400 ppm 10 Minutes 82.4 1.8 13.73 Surfactant 9 No treatment10 Minutes 72.2 2.2 14.88

The synthetic fibers used for each sample are bicomponent fibers ofCoPET/PET. The hydrophilizing agent utilized is TexCare™ SRN-240 and thesurfactant utilized is Triton-X 100 as available from The Dow ChemicalCompany.

As demonstrated by the above table, the synthetic fibers treated with ahydrophilizing agent may demonstrate lower contact angles and,therefore, durable wettability post washing when compared to the postwashing synthetic fibers treated with a surfactant.

Sustainable Wettability

A nonwoven fibrous structure may be analyzed for sustainable wettabilityin the following manner. The sample fibrous structure may be placed onan absorbent pad. Multiple insults of test liquid may be applied to thefibrous structure at timed intervals. Each insult of liquid may beconsidered as a strike-through. The strike-through times may then berecorded without changing the absorbent pad.

In one example, a nonwoven fibrous structure exhibits sustainablewettability if after saturating the fibrous structure with water (testliquid) multiple times (at least ten (10) times or more), the fibrousstructure still exhibits an HRC value of at least about 0.1 g/sec and/orat least about 0.2 g/sec and/or at least about 0.3 g/sec and/or at leastabout 0.4 g/sec and/or at least about 0.5 g/sec.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this written document conflicts with any meaningor definition of the term in a document incorporated by reference, themeaning or definition assigned to the term in this written documentshall govern.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A method for making a fibrous substrate, themethod comprising: depositing from a headbox onto a Fourdrinier wire aslurry comprising cellulosic fibers, from 10% to 30% synthetic fibers,and from 40 ppm to about 50 ppm of a hydrophilizing agent to form anembryonic web, wherein at least one of the synthetic fibers forms adurable association with the hydophilizing agent; de-watering theembryonic web to form a web having a consistency of at least 50%consistency; adhering the web to a surface of a Yankee dryer; andcreping the web off of the Yankee dryer after the web reaches aconsistency of at least 90%.
 2. The method of claim 1, wherein thesynthetic fibers are CoPET/PET bicomponent fibers.
 3. The method ofclaim 1, wherein said cellulosic fibers comprise Northern Softwood Kraftfibers.
 4. The method of claim 1, wherein said cellulosic fiberscomprise Eucalyptus fibers.
 5. The method of claim 1, wherein saidde-watering step is accomplished at least partially by vacuum assisteddrainage.
 6. The method of claim 1, wherein said de-watering step isaccomplished at least partially by through air drying.
 7. The method ofclaim 1, wherein said embryonic web is transferred to a photo-polymerfabric.